When To Plant Watermelon In Maryland

Knowing when to plant watermelon in Maryland is the single most important factor for a successful, juicy harvest. Get the timing wrong, and you risk losing your plants to frost or ending up with underripe fruit when fall arrives. This guide cuts through the guesswork to give you the clear schedule and tips you need.

Maryland’s climate varies from the cooler western mountains to the warmer coastal plain, but most gardeners face the same challenge: a relatively short growing season. Watermelons need a long, warm stretch to develop their signature sweetness. Planting at the optimal moment gives your vines the best possible head start.

The golden rule for planting watermelon in Maryland is simple: wait until all danger of spring frost has passed. Watermelons are extremely sensitive to cold soil and frost, which can stunt or kill young plants. Rushing to plant early rarely pays off.

For most of Maryland, the safe planting window for watermelon seeds or transplants is from mid-May to early June. Here’s a more detailed breakdown:

Western Maryland (Frost Zone): Aim for late May to early June. The higher elevations mean a later last frost date.
Central Maryland (Piedmont): The sweet spot is typically mid-May. Baltimore and Frederick areas fall into this range.
Southern Maryland & Eastern Shore: You can often start a bit earlier, in early to mid-May, thanks to milder coastal temperatures.

Always verify your area’s average last frost date. A great resource is the University of Maryland Extension. Once that date has passed and soil has warmed, you’re clear to plant.

Why Timing is Everything for Watermelons

Planting too early in cold soil causes seeds to rot and transplants to sit, stressed and vulnerable. Planting too late means your fruit won’t mature before the first fall frost. Watermelons typically need 70-90 days of warm weather to reach harvest, depending on the variety. Hitting that May/June window ensures they have it.

Starting Seeds Indoors vs. Direct Sowing

You have two main options for getting your watermelon plants started. Each has it’s pros and cons.

Starting Seeds Indoors

This method gives you a 2-3 week head start, which is valuable in Maryland. Here’s how to do it right:

Start seeds indoors about 3-4 weeks before your planned outdoor transplant date. For mid-May planting, start seeds in mid-April.
Use large, individual pots (3-4 inches) as watermelon seedlings hate root disturbance.
Plant seeds ½ inch deep in a seed-starting mix. Keep the soil warm (75-85°F) for best germination.
Provide plenty of light from a sunny south window or grow lights.
Harden off seedlings for a full week before transplanting them outside to acclimate them to sun and wind.

Direct Sowing in the Garden

This is simpler and avoids transplant shock, but your season starts later. Wait until soil temperature is consistently above 70°F. You can use a soil thermometer to check.

Prepare your planting hill or row after the soil is warm.
Plant 4-6 seeds in a small hill, about 1 inch deep.
Space hills 6-8 feet apart; watermelons need serious room to run.
Once seedlings emerge and grow a few inches, thin to the 2-3 strongest plants per hill.

Choosing the Right Watermelon Variety for Maryland

Selecting a variety suited to a shorter season is crucial. Look for “early-maturing” or “short-season” types, typically needing 75-85 days. Some excellent choices for Maryland include:

‘Sugar Baby’: A classic icebox type (8-10 lbs), maturing in about 75 days. Great for smaller gardens.
‘Blacktail Mountain’: Known for good cold tolerance and early ripening (70-75 days).
‘Yellow Doll’: A yellow-fleshed, early variety ready in about 68 days.
‘Crimson Sweet’: A larger, disease-resistant variety that still matures in a reliable 85 days.

Avoid giant, 100+ day melons unless you are an expert gardener with ideal conditions.

Preparing Your Garden for Watermelon Success

Watermelons are heavy feeders that demand sun, heat, and space. Proper site prep makes all the difference.

Site and Soil Requirements

Full Sun: Choose the sunniest spot in your garden—at least 8 hours of direct sun daily.
Soil: Well-draining, sandy loam is ideal. Amend heavy clay soil with generous amounts of compost to improve drainage and warmth.
pH: Aim for a soil pH between 6.0 and 6.8.
Nutrients: Mix in a balanced, slow-release organic fertilizer or well-rotted manure before planting. Watermelons need plenty of phosphorus and potassium for fruit development.

The Importance of Soil Warmth and Mulch

Since soil temperature is key, consider using black plastic mulch. Lay it over your planting bed 1-2 weeks before planting. It warms the soil, suppresses weeds, and conserves moisture. Cut holes to plant through it. If you prefer organic mulch, wait until the soil is thoroughly warm before applying straw around plants.

Caring for Your Watermelon Plants Through the Season

Consistent care after planting ensures healthy vines and well-formed fruit.

Watering and Feeding

Watermelons need deep, consistent watering, especially during fruit set and growth. Aim for 1-2 inches of water per week. Soak the soil deeply, then let it dry slightly before watering again. Avoid overhead watering to reduce disease risk. A mid-season side dressing of compost or a balanced fertilizer when vines start to run can give them a boost.

Pollination and Fruit Set

Watermelons produce separate male and female flowers. Bees are essential for pollination. If you notice small fruits forming but then turning yellow and falling off, poor pollination is often the cause. To encourage bees, avoid using pesticides during flowering. You can even hand-pollinate flowers using a small paintbrush if bee activity seems low.

Knowing When to Harvest Your Maryland Watermelons

Harvest time is usually late August through September in Maryland. Here are the classic signs of ripeness:

The Curly Tendril: The curly tendril closest to the fruit stem turns brown and dries up completely.
The Ground Spot: The spot where the melon rests on the ground changes from white to a creamy yellow.
The Sound: A ripe melon often (but not always) makes a deep, hollow sound when thumped.
Skin Texture: The rind loses its glossy shine and becomes dull, and it becomes tough to puncture with a fingernail.

Use a combination of these signs, especially the tendril and ground spot, for the best results. Once cut, watermelons do not continue to ripen further.

Common Problems and Solutions for Maryland Gardeners

Cool, Wet Weather: This promotes fungal diseases like powdery mildew. Choose resistant varieties, ensure good air circulation, and avoid wetting leaves.
Cucumber Beetles & Squash Bugs: These pests can damage vines and spread disease. Use row covers early in the season (removing them for pollination), and hand-pick pests.
Poor Fruit Development: Often due to inconsistent watering, lack of pollination, or nutrient deficiency. Focus on consistent soil moisture and bee-friendly practices.

FAQ: Watermelon Planting in Maryland

Can I plant watermelon in July in Maryland?

Planting watermelon from seed in July is generally to late for most of Maryland, as the fruit will not mature before fall frost. However, you could try planting an extremely fast-maturing variety (under 70 days) in early July if you use a transplant and are in a warmer region.

What is the best month to plant watermelon?

For Maryland, May is the best month to plant watermelon. This provides the long, warm growing period the plants require.

How long does it take for watermelons to grow?

From planting to harvest, most watermelons need 70 to 90 days. Always check the “days to maturity” listed on your seed packet or plant tag and count from your planting date.

Can I use a greenhouse to start watermelons earlier?

Yes, a greenhouse or cold frame is excellent for starting seeds or growing transplants. You can gain several extra weeks. Just remember to harden off plants thoroughly before moving them to the permanent garden bed to avoid shock from the change in conditions.

By following this schedule and tips, you align your gardening efforts with Maryland’s unique climate. Patience in spring leads to the reward of sweet, homegrown watermelon in late summer. There’s nothing quite like the taste of a melon you’ve nurtured yourself from a tiny seed to a ripe, heavy fruit.